Credit Card Interest Impact Calculator

How credit-card interest snowballs

Credit-card revolving debt uses monthly compound interest: debt(n) = debt(0) · (1 + i)^n, where i is the monthly rate. At 10% per month, R$ 2,000 unpaid becomes R$ 3,797 in 7 months — almost double. At 6% per month, it doubles in 12 months. The math is identical to the compound-interest formula for savings, except now you are on the losing side.

Brazilian context: until 2023 the revolving rate often exceeded 400% per year. After the National Monetary Council (CMN) intervention, the legal cap is now 100% of the original debt — that is, total interest plus charges cannot exceed the original amount. Even so, rates around 10-15% per month are still common. Installment-of-bill plans ("parcelamento da fatura") sit at 8-15% per month and are usually offered by the issuer before falling into outright revolving credit.

Brazilian context and ways out

The "credit-card snowball" is the most common financial pitfall in Brazil. Standard ways out: portability to a CDC (personal-loan line, typically 3-6% per month), payroll-deductible loan ("consignado", 1.5-2.5% per month for civil servants and retirees), or migrating the balance to a digital bank with lower rates. Law 14.181/2021 ("Superendividamento") allows debt renegotiation at Procon. Serasa Limpa Nome runs periodic discount campaigns reaching up to 99% off arrears.

FAQ

What is the difference between revolving credit and installment of the bill? Revolving credit is the automatic line that kicks in when you pay less than the full bill; rates are the highest in the system. Installment of the bill is an offer made by the issuer to split the unpaid amount into fixed installments at a contractually defined rate, usually lower.

Can the bank charge more than 100% of the original debt? No — after the 2023 CMN rule, total charges (interest, fees, IOF) on revolving balances cannot exceed the original debt amount.

Does paying the minimum solve the problem? No — paying only the minimum keeps the unpaid portion in the revolving line at the highest rate in the market. It buys time but increases the total cost.

Does negotiating affect my Serasa score? Renegotiating removes the active default from your record and starts to recover the score within 30-60 days, but the negative history remains visible to creditors for up to 5 years.